[n8dgr84]

After having bought the "CDV Free" clutch slave 2 years ago, I finally got around to changing the CDV out, but I didn't even have to use the new clutch slave.

Kern417 made a great video showing how to do it for FREE11!!1!
https://www.youtube.com/watch?v=CFict1fzerE
All you need is to get the central under panel off with 8mm and 10mm.

For this job, you'll need:
-#8x3" wood screw
- locking plyers
-13mm socket
-3/8" ratchet and short extension

Benefits of this mod:

The driveability benefits are numerous:
- less clutch slippage between shifts which makes engagement quicker and puts less wear and tear on the clutch so it should also last longer

- less whiplash on engagement if you know how to shift and don't have to wait so long for the CDV to bleed out so you can keep up with traffic easier

- quicker engagement means on fast shifts it retains more boost between gears (without powershifting). I was able to maintain 6psi boost which made the car accelerate much faster. I felt like I hit a 50 shot of nitrous compared to how it was before. This was a benefit I never expected with this mod but I think it is legit and it makes sense. I always felt like the throttle tip-in on shifting was soft on this car so I'm hyped that this made a huge difference. This is one of those things that doesn't require higher octane, a more aggressive tune, or have any real negative consequences (so long as you're not dumping the clutch at every stop light, shocking the drivetrain.)

Overall 11/10 mod because it's free and helps with performance and reduces clutch wear.

Update: pedal was a bit soft so I bled the clutch line with my Motive Power Bleeder (M2 uses same reservoir for clutch and brakes). Fluid was dark so I'm glad I did. I would suggest bleeding the clutch line as part of this mod.

[AlpsRider]

Thanks for the video. It was clear and easy to follow. I think I may do this mod myself when I get a warm day.

[n8dgr84]

Originally Posted by AlpsRider

Thanks for the video. It was clear and easy to follow. I think I may do this mod myself when I get a warm day.

The only thing I would add is that I had to bleed the clutch line as it got a bit soft (but still worked.) Luckily I had some SRF leftover and a Motive bleeder.

[mike@x-ph.com]

[tokki]

Conservatively, I would not recommend doing this. BMW engineers and particularly, M engineers, are smarter than you. It is there to serve a purpose. It feels snappier because your essentially releasing the clutch more abruptly, which will wear and tear your mechanicals a lot faster. Another thing to consider is one of the reasons why MT6 is less prone to crank hub slippage than AT is because of these clutch characteristics.

[Telluride]

Originally Posted by tokki

Conservatively, I would not recommend doing this. BMW engineers and particularly, M engineers, are smarter than you. It is there to serve a purpose. It feels snappier because your essentially releasing the clutch more abruptly, which will wear and tear your mechanicals a lot faster. Another thing to consider is one of the reasons why MT6 is less prone to crank hub slippage than AT is because of these clutch characteristics.

Fair. If one's manual transmission skill is weak and rev matching is not their forte. It's a nannie and while I understand your logic, not sure I'd go as far as your crank hub theory.

Otherwise, I removed my cdv and appreciate the more direct clutch engagement and improved 1st to 2nd shift.

[medphysdave]

I swapped to a valve that doesn't have the CDV. Like most mods I immediately noticed it and within a day I adapted and now couldn't tell you what it was like to drive the car with a CDV. It would be interesting to drive someone's stock car without CDV delete, UCP, and AS shifter.

[Telluride]

Originally Posted by medphysdave

I swapped to a valve that doesn't have the CDV. Like most mods I immediately noticed it and within a day I adapted and now couldn't tell you what it was like to drive the car with a CDV. It would be interesting to drive someone's stock car without CDV delete, UCP, and AS shifter.

Agreed. Having only driven manuals since I got my license, I noticed the difference when I picked up my car sans cdv removal. But without doing a drive 'with a cdv' and 'without a cdv' back-to-back... yeah, it would be imperceptible.

However, when I first got my car (with the cdv installed) and experienced running it through the gears at full fury, shifting just prior to hitting the rev limiter... I wondered if my left foot was riding the clutch pedal between my 2nd to 3rd or 3rd to 4th upshifts. Being my first BMW and ignorant of a cdv, I definitely questioned if I had forgot how to drive a stick!

[Westersund]

BMW makes cars for everyone, everyone can't engage the clutch properly.

I prefer driving without a CDV and the delayed reaction it produces, haven't removed it on the M2 yet though.

[donkey]

Originally Posted by tokki

Conservatively, I would not recommend doing this. BMW engineers and particularly, M engineers, are smarter than you. It is there to serve a purpose. It feels snappier because your essentially releasing the clutch more abruptly, which will wear and tear your mechanicals a lot faster. Another thing to consider is one of the reasons why MT6 is less prone to crank hub slippage than AT is because of these clutch characteristics.

I haven't done a CDV delete yet, but I don't buy that it reduces wear & tear that much.

If the clutch engagement was more predictable and linear, I'd be on the clutch a lot less because I'd be more certain when it engages and could build up better/more precise muscle memory. As it is now, it's kind of a crap shoot. Obviously you don't want to be on it too little because then you run into driveline shock, but there's a good middle ground, which in some MT cars is very easy to find.

Engineering is rarely just making the most optimal decisions. There's cost, customer feedback, deadlines, and decisions from management all playing a factor. In that sense I think the CDV is a perfect example of good engineering, but a bad end result.

[///MPhatic]

I've considered doing this many times, but with the way I drive the car I don't think it's necessary. If I do it, I'll want it all, which is NO MORE DAMN REV HANG, and a lighter flywheel. This car loses revs so terribly slow, and it bugs the isht out of me.

[medphysdave]

Originally Posted by ///MPhatic

I've considered doing this many times, but with the way I drive the car I don't think it's necessary. If I do it, I'll want it all, which is NO MORE DAMN REV HANG, and a lighter flywheel. This car loses revs so terribly slow, and it bugs the isht out of me.

I like the rev much for around town driving, but on track I don't like it as much during corner entry and slowing down. There's something unnatural about it. Recently I noticed that some of my lack of smoothness during shifts come from what must be my lazy foot position. I rest my heel on the floor and pivot my foot forward to press clutch. I noticed when I lift my foot off the floor and then do the clutch work it led to much smoother shifts. I'm not sure exactly what the difference is. Maybe it's how quickly I'm actually pressing and depressing the clutch with the two different foot positions? Pressing more with part of shoe/foot that can flex. Not sure, but it's interesting.

I do think there are situations where the CDV and rev hang compound on each other. Especially during attempts to quick down shifts.